Cushioning device for cylinders



Jan. 27, 1959 H. c. HALLERsTRoM 2,870,744

CUSHIONING DEVICE FOR CYLINDERS I Filed Feb. 1e, 195e v 2 sheets-sheet 1 v xg Niki/@darf .J/aro//c Cflijrom,

Jan., 27, 1959 H. c. HALLERSTROM 2,870,744

CUSHIONING DEVICE FOR CYLINDERS Filed Feb. 16, 195e v l 2 sheets-sheet 2 United States Patent-v O CUSHIONING DEVICE FOR 'CYLINDERS Harold C. Hallerstrom, Evanston, lll., assignor to Hanna Engineering Works, Chicago, Ill., a corporation of Illinois Application February 16, 1956, Serial No. 565,849l

6 Claims. (Cl. 121-38) The invention relates to fluid power cylinders and has reference in particular to a new and improved cushioning device carried by the piston of the power cylinder and which can be rendered effective for cushioning the piston stroke at each end of the cylinder or at one end only.

An object of the invention is to provide a simple but effective device for cushioning the piston of a tiuid power vision of a cushioning device for fluid power cylinders which will be slidably carried by the piston of the cyli'nder so as to project from its respective sides of the piston and which will provide valve membersfor contact with the end walls of the cylinder for trapping fluid between the piston and the cylinder walls whereby to cushion the stroke of the piston together with its load.

A further object of the invention is to provide a power cylinder cushioning device wherein various cushioning lstroke lengths can be obtained by changing the length of the slidable rods carried by the piston and which have the valve members secured to the respective ends thereof.

A further object is to provide a piston cushioning device for use in iluid power cylinders which will give the maximum cushioning effect over the lentire length of the cushioning stroke, which will give full pipe ow to the piston area at the start of the return stroke, and which will be fully adjustable so that the intensity of the cushioning action can be varied.

With these and variousy other objects in View the invention may consist of certain novel features of construction and operation as will be more fully described and particularly pointed out in the specication, drawings and claims appended hereto.I

In the drawings, which illustrate an embodiment of the invention, and wherein like reference characters are used ice with end member 11 and for sealing purposes the packing Figures 4 to 8 inclusive are sectional views illustratingl ment of the invention includes the tubular cylinder 10 diagrammatically the cushioning action of the present del vice during a piston stroke in one direction.

ring 13 is provided. As a result thereof this left end of the tubular cylinder 10 has communicating relation with the central bore 14 formed in end member 11 and vwhich in `turn joins with passage 15 throughwhich a uid pressure can be supplied to the cylinder and discharged therefrom. In a similar-manner the right hand end of the tubular cylinder 10 has intertting relation with end member 12, the parts being eectively sealed by the packing 16. A central passage 17 extends through the center Vof end member-12 and thev central passage in turn has communicating relation with passage 18 through which a fluid under pressure is delivered to and discharged from the cylinder. Theend members 11 and I12 vare suitably connected by tie rods 20 which extend through openings in ange portions 21 and areheld in connected relation by the threaded nuts 22. The tubular cylinder 10 and the end members 11 and 12 are accordingly ixedly held in associated relation to forma unitaryassembly and which is preferably mounted on a fixed support so that the reciprocations of the pistonand piston rod of the power cylinder can be caused to perform'its Vintended work.

The numeral 24 indicates the piston in its entirety, Figures l and 2, and the numeral 25 indicates the piston rod which has a fixed connection to the piston by means of structure to be presently described. The piston rod extends through passage 1'7 of the forward end member 12 and this passage is exteriorly closed by means of the gland nut 26 releasably secured to the end member 12 by securing screws 27 and which -has'a slidable fit with the piston rod 25. The gland nut 26 provides a scraper 28 having encircling relation with the piston rod and which is operative for removing dirt from the piston rod so as to protect the rod bearing and lengthen the life of the packing 29. The packing 29 preferably comprises rod packing of the self-adjusting type including a plurality of standard V rings in combination with a metal adapter.- With the gland nut 26 secured on end member 12 the power cylinder is closed except for id passages 15 and 18, although the piston rod 25 is'free to reciprocate without losing any of the pressure iluid along the rod by reason of the packing 29.

At its terminal end the piston rod 25 is reduced in diameter as at 30 and said reduced end is threaded'as at 31. The piston 24 isV formed with a central bore 33 extending through the piston and which central bore I eceives the reduced end 30,.the threaded end 31 extending beyond the bore 33 and receiving the securing nut 3 4. Each end of the piston is recessed,with the recess' formed in they left hand end of the piston being indicated by numeral 35 and the recess formed in the 'right hand end being indicated by numeral 36. It will be noted that the securing nut 34 has location within recess 35 at the left hand end of the piston, whereas, plate 37 is located in the base of recess 36 for the purpose of retaining the packing rings 3S and 39, the utility of which will be presently described. An additional packing ring of somewhat larger size, indicated by numeral 40, is positioned within groove 41 and said ring has encircling 'relation With the reduced portion -30 of the piston in order to seal the passage 33 toprevent flow of pressure uid from one side of the piston to the other` Additional sealing means in the form of special Ysealing rings `of rubber, suchY as 42 and 43, are provided and are located in grooves on the cylindrical surface of the piston and which have contact with the inside cylindrical wall of the cylinder for sealing the piston with respect to said cylinder Walls. The packing rings"'42 and 43 are preferably V- shaped in transverse section and it will be observed that ring 42 is directed 'toward the left, whereas ring 43 is stroke by trapping some of the 'fluid 'between the piston land a'n end of the cylinder. The device essentially con- 'sists of a left hand valve member '44 and a 'right hand valve member 45u-each valve member presenting a at exterior surface "such as'46 and 47, respectively, and each valve member in combination with the flat exterior sur- V'fa'ce being provided with a sealing ring such 'as 48 and 50.

`When the 'piston 24 is at the end of its stroke in a left Yhand direction the valve member '44 is located within recess 35 formed in the left end of the pis-ton. When the piston is located at 'the end of its stroke in a right hand i idirection valve member 45 will be located within recess 36 formed VAin Ythe right hand end of lth'e piston. Accordingly, 'valve members 44 and 45 have certain structural characteristics which are similar. However, with this exception their physical shape is quite diierent. This is 'due to Ythe fact that since `valve member 44 fits within re- 'cess 35 it is vnecessary to provide a central cavity such as 51 onthe inside surface of this valve member for receiving the projecting threaded end 31 of the piston rod and for also receiving the securing nut 34 which assists in securing said piston rod to the piston. Since valve member `45 is mounted on piston rod 25 'so as to have 'slid- 'able movement on the piston rod, thesaid valve member -i's lprovided with a central passage 52 through which the piston rod extends, Y'and the valve member is additionally :provided with the `packing ring 53 `having'encircling relation with the piston rod for eiecting a Huid-tight seal therewith.

The'valve members J44 and 45, although having location von respective sides-of thepiston 214, are suitably connected to leach other .by Ameans ofthe valve member tie rods A55 and :56. Said valve member'vtie rods extend through openings .in the piston such as -57 "and 458, respectively, the

:openings being concentric ywith the packing rings 38 and Y" `39` retained fin place by the plateY 37, as previously 'described. The valve member tie -rods 55 and 56 are therefore slidable with respect to piston '24 although having ya pressure-tightumountin'g in the piston due tothe sealing action of rings 38 and 39. The'valve member 44 is bored at spaced locations for receiving the ends of the valve member tie rods v55 and 56for which purpose the lends `project beyond the .central section of -the piston and into vthe recess 35. A circumferential groove such 'asA 60 is formed in the exterior 'Wall of Valve'member144 and a retaining ring 61 is located in Vsaid groove and in slots formed in the valve member 'tie rods 55 Vand 56, respectively.

Accordingly, the .retaining ring A61 functions as a locking member to hold the valve member tie rods in operative assembled relation with the valve Vmember 44 and in order to prevent displacement of the retaining ring 61 stop ,pins 62 and 63 are provided and which have location at `the respective terminal ends of the retaining ring 61. Thus 'the retaining'ring is held against rotation Within groove 60. However, the :same can be removed in order to `release the valve .member tierods by expanding the ring andrspringing the same loose'from the valve member 44. For this purpose "the Vretaining ring is'flexible Vand has v the ability to expand Iand contract to var-y the effec- 4 tive diameter of the retaining ring. hand ends of the valve member tie rods 55 and 56 are received in openings formed in the valve member 45 and in a similar manner the circumferential groove 64 receives the retaining ring 65 which coacts with slots formed in the valve member tie rods for releasably locking the valve member 45 to said valve member tie rods. The retaining ring 65 isheld Vagainst angular displacement by means of the stop pins66 and `67.

Each end member is provided with a fluid metering valve for adjusting the intensity of the cushioning action on the piston. The metering valve for end member 11 is indicated by numeral 70 and the metering valve for end member 12 is indicated by numeral 71. Valve 70 is located in passage 72 leading from the central passage 14 and the passage 72 is also in communicationwith the orice 73. The lower end of valve 70 is threaded at 74 for threaded connection with the end member 11 and the tapered end 75 will permit varying amounts of uid to escape to the passage 14, depending on the position of valve 70 with respect to the orifice 73. The indicating disc 76 has indicia marked thereon so that as the valve 70 is rotated the particular cushion speed setting for the position of the valve is indicated. The valve member 71 has location within passage 77 in end member 12 and is threaded at '78, the said passage 77 communicating with passage 17 and with the orifice rS0. The indicating disc 81 indicates the cushion speed setting for the various r tative positions of the valve member.

The valve members 44 and 45 are each releasa'bly connected to the valve member tie rods 55 and 56 at respective ends of the valve'member tie rods and the valve member tie rods are in turn mounted by the piston 24 for slidable movement with respect vto said piston. Accordingly, Vwhen the piston is located adjacent end member 11 the valve member 44 will `be located within recess 35 and when the piston is located adjacent end member 12 the valve member 45 will be .located within recess 36. The operation of the cushioning vdevice can best be understood by reference to Figure l, and Figures 4 to 8 inclusive, the latter figures illustrating diagrammatically thel position ofthe various parts 'during one complete stroke of the piston. As shown in Figures l and 4, the piston is located in its extreme left hand position in contact with end wall 63, of end member 11; The at'surface 46 of valve member 44 is also in contact with wall 68 and due to the flat contacting surfaces of the parts, together with the sealing ring 48, the bore 14 and passage 15 are effectively sealed with respect 'to the tubular cylinder 10. The piston is now in 'a position to start a working stroke ina direction to the right and upon pressure fluid being 'admitted to passage 15 the same will exert a force on valve member 44 equal to the area exposed by the 'central bore 14 times the pressure of the fluid.

In accordance with the invention'the valver member 44 has a certain amount of clearance or play with respect -to the depth of the recess 35, asfindicated by x, Figure 2. Y In other words, the thickness 'of valve member 44 is less than the depth ofthe recess by the amount of the clear ance indicated by x vand when zthe force as above eX plained isA exerted on valve 44 its initial movement will take up 'said clearance, see Figure 5. YThe initial shifting of the valve member 44 permits the pressure ytluid'to exert its elfect 'upon substantially the entire face ofthe piston and the piston therefore has a Vrapid acceleration in its movement toward the right.

ln Figure 6 the piston and cushioning device are moving toward the right, with the 'piston being located `substantially in mid-position as regards cylinder 10,'fin which `pition the cushioning device has not as yet become 'eiective )In Figure 7 the'piston has moved to theright a sulicient distance to cause 'contact of valve member V45 with end member 12. More particularly the'at sur- 'face 47 of -valve member '45 is in contact with the -llat surface 69 provided -by 'end member 12 and thus passage The opposite right i 17 is completely sealedoif, with the result that fluid 'which had heretofore been discharging through passages is pushing the pistonplus the pressure resulting from overcoming the inertia of the weight of the load attached to the piston rod. Eventually the piston and cushioning device will be positioned as shown in Figure 8 wherein it will be observed that the parts are ready for a piston stroke in a left hand direction. During this return piston stroke the action of the cushioning device is the same as described and the piston movement is cushioned to an extent as predetermined by the setting of the valve member 70.

Various cushioning stroke lengths can be obtained by using longer or shorter valve member tie rods. In fact, it is possible to obtain a cushioning stroke length equal to any part of the piston stroke without the length of the cylinder itself Ebeing affected. Although each stroke of the piston is positively and adequately cushioned, nevertheless the piston will respond on its return stroke to full iluid pressure and acceleration will be rapid until the cushioning device again becomes effective.

On each stroke of the piston the cushioning device is carried by the piston for a part of the stroke and for the remaining part of the stroke the piston has movement with respect to the cushioning device, lwhich is held .against movement since one of its valve members will be in contact with an end member. The present `cushioning device is further characterized in that one valve member is mounted for slidable movement on the piston rod. `Also it can be noted that the maximum length for the valve member tie rods may be such as to space the v-alve members a distance equal to the distance between the end members.

The invention is not to be limited to or by details of construction of the particular embodiment thereof illustrated =by the drawings as various other forms of the device will of course lbe apparent to those skilled in the art without departing from the spirit of the invention or the scope of the claims.

What is claimed is:

l. In apparatus of the character described, a iluid power cylinder having end members provided with passages for admitting a pressure luid to the cylinder and for exhausting the fluid therefrom, means for cushioning the impact of the piston of said cylinder with Athe end members at the end of the piston strokes, said means including a valve member located on each side of the piston, said piston on each side thereof having a recess for receiving the valve member on that side, each valve member having a flat face for valving contact with lthe flat surface of its respective end member whereby to `close the duid passage in the end member, and tie rods connecting the said valve members, the tie rods extending through the piston and 'being slidably mounted thereby so that the valve members and tie rods comprise a unitary assembly capable of movement with respect to the piston, whereby during each stroke of the piston one valve memvber or the other is caused to contact its respective end member to close the fluid passage therein and trap duid between the piston and the end member, each recess in the piston having a depth greater than the thickness of the valve member to be received therein so that prior to the start of each piston stroke initial movement of a valve member takes place as permitted by the depth of its recess to admit pressure Huid to substantially the entire face of the piston, and a lmetering valveprovided by each end member .and operative to release the trapped uid at a predetermined metered rate whereby the travel of the piston is cushioned to the extent desired.

2. In a duid power cylinder, a cylinder, an end mem- Iber at each end of the cylinder, ports in saidend members connected to a source of fluid power, a piston slidable in said cylinder, a piston rod secured to said piston and slidably guided through one of said end members, means carried by said piston and piston rod for cushioning piston impact with said end members, said cushioning means comprising a pair of valve members, said valve members 'being on opposite sides of said piston and c0- acting to selectively close the port in the adjacent end member, said Valve member on the rod side of the piston being sealingly slidable on said piston rod, means for connecting said valve members together and supporting same on said piston, and means at each end of the cylinder for controlling the exhausting of iiuid upon movement of the piston towardone end of the cylinder and closing of the port at that end by the corresponding valve member.

3. In a fluid power cylinder, a cylinder, an endmember at each end of thecylinder, ports in said end mem- Ibers connected to a source of fluid power, a piston slidable in said cylinder, a piston rod secured to said piston and slidably guided through one of said end members, means carried by said piston and piston. rod for cushioning piston impact with said end members, said cushioning means comprising a pair of valve members, said valve members being on opposite sides of said piston and coacting to selectively close the port in the adjacent end member, said valve member on the rod side of the piston being sealingly slidable on said piston rod, means for connecting said valve members together and supporting same on said piston, and means in each end member for controlling the exhausting of duid upon movement of the piston toward one end ofthe cylinder and closing of the port at l that end by the corresponding valve member.

4. A duid power cylinder as defined by claim 3, wherein said control means in each end member comprises a metering Valve.

5. In a fluid power cylinder, a cylinder, an end member at each end of the cylinder, ports in said end members connected to a source of duid power, a piston slidable in said cylinder, a piston rod secured to said piston and slidably guided through one of said end members, means carried by said piston and piston rod for cushioning piston impact with said end members, said cushioning means comprising a pair of valve members, said valve members being on opposite sides of said piston and coacting to selectively close the port in the adjacent end member, said'valve member lon the rod side of the piston p said valve members secured .to opposite ends thereof, and

means in each end member for controlling the exhausting of duid upon movement of the piston toward one end of the cylinder and closing of the port at that end by the corresponding valve member.

6. A fluid power cylinder comprising, a cylinder, an end member at each en d of the cylinder, ports in said end members for admitting a pressure fluid to the cylinder and for exhausting 'the fluid therefrom, av piston slidable in said cylinder, a piston rod secured to said piston and slidably guided through one of said end members, said piston having recessed end portions, a cushioning device including a pair of valve members, said valve members 'being on opposite sides of said piston and coacting to selectively close the port in the adjacent end member, said valve members being concentric -to'said cylinder and the valve member on the rod side of the piston being sealingly slidable on said piston rod, said valve members' l valve members movetogcther reiativerto said piston, and

means at each endrof'the cylinder for controlling the cX- Yhausting of. uid upon movement of the piston toward one end of the cylinder and closing ofthe port at that end bythe corresponding vagive member.

References Cited inthe le of this patent UNITED STATE-s PATENTS Dapron Oct. 26,` 1926 Loewe '.Y T June 12, 1951 Anderson Oct. 3,0, 1956 Tucker Mar. 26, 195'7 

